An image forming apparatus adopting the electrophotographic method transfers an image formed on a photoreceptor drum onto a sheet, and then heats and presses the sheet to fix the toner image on the sheet. In the image forming apparatus adopting the electrophotographic method, toner should be supplied when toner is used up. For this reason, the image forming apparatus adopting the electrophotographic method is generally configured to use a replaceable toner cartridge in which expendable toner is stored.
A known toner cartridge includes a stirring paddle that stirs the toner stored in a toner storage container and an auger screw that conveys the toner stored in the toner storage container to a discharge port communicating with the developing device body (for example, see JP-A-2011-081215).
The toner cartridge has a vertical wall that is perpendicular to the axis of the auger screw and is provided at a downstream end along the toner conveyance direction where the auger screw is rotatably supported. Thus, when the toner is conveyed to the vertical wall by the auger screw, the toner in the side of the discharge port falls by gravity. In contrast, the toner in the side opposite to the discharge port is likely not to fall, and thus tends to accumulate near the wall. When toner is continuously conveyed under such state, the toner is pressed against the vertical wall to be dense, and an excessive load is applied on the auger screw. As a result, the auger screw stops its rotation, and for example, tooth-skipping or the like might occur at a gear that transmits a driving force to the auger screw.